Quantum Cryptography with Photon Pairs

Publisher Website
Google Scholar
Abstract
Photons, randomly prepared in one of two non-orthogonal quantum states, are used for a cryptographic key distribution. If the receiver tests them one by one, he may either identify their state, or get an inconclusive (useless) result. If he tests them pairwise, he may also obtain information about their parity (whether or not they have the same state), without identifying each signal separately. While this procedure does not give a higher rate of information transmission, the parity-generated bits are more sensitive to attacks by an eavesdropper than bits obtained from single photons.